The weapons tests have been accompanied by a spike in hostile North Korean rhetoric including a threat to attack Washington and turn South Korea into a "sea of fire" and a repudiation this week of the 1953 Korean War armistice.
This week North Korea's official news agency threatened to destroy South Korea in a "sea offire, " and "reduce everything treacherous and anti-reunification to debris and build an independent, reunified country on it, " if any country dares to attack its nuclear installations.